As a social situation such as security is getting worsen, needs for grasping a congestion degree of a crowd from a video of a monitoring camera are increased for the purpose of safety ensuring and congestion reducing. In particular, there is a need to detect an urgent congestion as much as movement is restricted in order to secure safety of the crowd such as a station platform. In addition, there is a need to display a congested situation in quantification using a “crowd density” (the number of persons per unit area).
As a method of estimating the crowd density in quantification, PTL 1 discloses a technique of calculating a congestion degree from a relation between a feature quantity such as the number of corners and an edge quantity in an image and the number of persons.
NPL 1 discloses a phenomenon that a magnitude of a horizontal swaying is increased at the time of walking as the crowd density is increased. In addition, there is disclosed a description about a histogram which is an index of the congested situation using the phenomenon.